For medial gowns which require water repellency, a hydrophobic substrate such as a polypropylene nonwoven fabric is used. Further, medical gowns also require the antistatic property and the alcohol repellency. Accordingly, in order to impart the alcohol repellency, a hydrophobic substrate is treated with a fluorinated water repellent containing a fluorinated copolymer. Further, in order to impart the antistatic property, the hydrophobic substrate is treated with an antistatic agent. Further, as the antistatic agent is hydrophilic, the water repellency of the hydrophobic substrate itself is lowered when treated with the antistatic agent, and the decrease in the water repellency is suppressed by the fluorinated water repellent used in combination.
Recently, EPA (US Environmental Protection Agency) has pointed out that a compound having a perfluoroalkyl group (a perfluoroalkyl group will be hereinafter referred to as a RF group) having at least 8 carbon atoms is likely to be decomposed in the environment or in vivo, and the decomposition product is likely to be accumulated, i.e. it presents a high environmental impact. Therefore, a fluorinated copolymer for a water repellent composition, which has an RF group having at most 6 carbon atoms and having no RF group having at least 8 carbon atoms has been required.
As a water/oil repellent composition containing such a fluorinated copolymer, the following water repellent composition has been, for example, proposed.
A water repellent composition comprising a fluorinated copolymer having structural units based on a (meth)acrylate having a C6RF group, structural units based on a (meth)acrylate having a C8-40 alkyl group and structural units based on vinylidene chloride (Patent Document 1).